Telephone-exchange system



June 24, 1930 A. E. LpNDELL ET L I TELEPHONE EXCHANGE SYSTEM m SE A W R R m QQ M M Kg M Qw Q N ww A 7 mm 9. \MWVIIE m v m a m Wm (wa 7 Qm 1 Filed July 27, 1925 //7 l//7/'0/-5-' A/en E. Lynda/A fdqar H. C/ar/r. by #173 Jun 24, 1930: A. E. LUNDELL Er AL 1,767,854

' Y TELEPHONE EXCH ANGE sys'rnu Filed July 2'7, 1925 9 Sheets-Sheet 4 Mary/rial June 24, 1930.

A. E. LUNDELL ET AL 1,767,854 I TELEPHONE EXCHANGE SYSTEM Filed July 27, 1923 9 Sheets-Sheet 5 Sender A2,?

by v 2 1 June 1930. .A. E. LUNDELLETAL 1,767,

TELEPHONE EXCHANGE SYSTEM Filed July 27, 1923 9 Sheets-Sheet e dqar H. 6/ar/r by MAI/1 Jun 24 1930 A. ELQNDE'LLH'AL 1,167,854

TELEPHONE EXCHANGE SYSTEM Filed July 27. 192:5 9 Sheets-Sheet a WP I 3% N3 o 3.

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Patented June 24, 1930 UNITED STATES PATENT OFFICE ALBEN E. LUNDELL, OF NEW YORK, AND EDGAR H. CLARK, OF RIGHMON'D'HILL, NEW YORK, ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK v I v I TELEPHONE-EXCHANGE SYSTEM Application filed July 27,

. This application is a continuation in part of the application of Lundell and Clark,

vSerial No. 301,891, filed June 5, 1919.

This invention relates to automatic telephone exchange systems and more particularly t0 semi-automatic telephone systems in which an operator at the. central ofl ice receives a call manually and extends it through automatic switches.

The object of the invention is to provide a controlling equipment at a manual exchange by means of which the automatic selection of a wanted subscriber at a mechanical exchange may be controlled by an operator.

Formerly it was the general practice for the operator at the semi-automatic exchange to assign, by means of a call wire, an idle trunk to the manual operator who, by means of an ordinary cord circuit, extended the connection of a calling subscriber over the assigned trunk to the semi-automatic operator, who in turn by means of an impulse transmitting mechanism and automatic switches completed the connection to th wanted subscriber.

This invention is especially directed towards the provision of an improved central equipment by means of which a manual operator, after receiving the wanted number, automatically selects an idle trunk leading to the exchange in which the wanted subscriber is located, and by means of which the automatic switches at the exchange are controlled to extend the connection to the wanted subscribers line. The operator connects the selected trunk with the calling subscribers line by means of an ordinary cord circuit and the control equipment reverts to common use when the connection is completed to the wanted subscribers line.

It is the purpose of this invention to eliminate the use of a call wire connection between a manual and automatic exchange, and the service of the operator in the auto matic exchange in setting up a connection to a subscriber, thus eifecting a considerable saving of time for completing a connection and cost of equipment and operators.

One feature of this invention is the pro- 1923. Serial No. 654,106.

vision of a plurality of connecting units to which an idle trunk leading to an automatic exchange, an idle register and controlling equipment and an operators number selecting equipment may be connected.

Another feature is the provision of an indicating device by means of which the number of the selected trunk may be displayed to the operator.

Another feature is the provision of a starting and number selecting equipment by means of which a connecting unit is associated with a calling operator and by means of which the register and controlling equipment may be manipulated to control the selection of the wanted subscribersnumber.

Another feature resides in the provision of an allotting equipment whereby an idle connecting unit is assigned for use by a calling operator: in the fact that an individual allotting mechanism is associated with the trunks leading to a particular mechanical exchange; in the accessibility of all allotting mechanism by any operator and in the selective allotting of connecting units to oper ators where several operators simultaneously connect controlling means to the same allotter.

Another feature resides in the ability of the sender to automatically restore selector; switches to their normal position, when they involved in these units which will be set forth in the following description of a preferred embodiment of the invention.

It will be obvious to those skilled in the art that this invention is not limited to the particular type of equipment disclosed, but is applicable to systems employing other well known switching and indicating devices.

Figure 1 illustrates diagrammatically the general outline of an organization at a manual exchange in which a system embodying thevarious features and equipments of change is provided with a set of keys on which the wanted number may be registered, and an indicator for the display of the designation of the mechanical exchange and the trunk chosen for the extension of a call.

There is provided for the common use of all operators a group of connecting units for each of the groups of trunks leading to a mechanical exchange and a group of registering and controlling equipments accessible to all operators through the medium of any one of said connecting units. Each connecting unit consists of three automatic switching mechanisms. One of these mechanisms will be termed an operat'ors finder switch and is provided for the purpose of associating the key-set and indicating equipment ofany operator with the connecting, unit. A second mechanism that will be termed a trunk selector is provided for the purpose of associating the connecting unit with an idle trunk of the group leading to the desired mechanical exchange, and a third mechanism that will be termed a sender selector is for the purpose of associating an idle registering and controlling equipment or sender with the connecting unit. All of the senders are accessible to any one of said connecting units. 3

An allotti-ng and controlling mechanism 'is provided for each group of connecting units. This mechanism consists of an ex change key for each mechanical exchange at each operators pos1t1on, and an allotter switch controlled by the associated exchange keys in any operators position to allot an idle connecting unit for the use of the op crater desiring a connection to the correcuit in combination with one of these connecting units. The operator ascertains the wanted number from the calling subscriber and then associates the keys and the trunk indicator with an idle connecting unit of a group of trunks leading to the desired exchange. The connecting unit is also automatically connected to an idle sender. The finding of an idle trunk leading to the wanted exchange and the indicating of the number of the chosen trunk on the trunkindicator is automatically performed. The operator then proceeds, after having received a dialing tone indicating that an idle sender has been associated with the keys, to manipulate the keys and adjust the sender in accord nee with the number wanted. In response tothe operation of the digit keys the usual selector switches at the mechanical exchange begin to operate and associate; the selected trunk with the wanted subscribers line. During the operation of the selector switches at the mechanical oflice, the operator connects the outgoing end of the cord circuit associated with the calling subscribcrs line, with the selected trunk, and when the selectiveoperations. at the mechanical exchange are completed, the wanted subscriber is signalled in the usual manner and the connecting unit is released and made accessible for a second call.

The selector switches and circuits that may be used in connection with this invention, are well known in the art. Suitable selector switches are shown in Figs. 8 and 9. Their description, however, will net be carried forward with the operating features of this circuit but will be described separately to facilitate a clear understanding of the release features in connection with abandoned calls. A suitable arrangement that may also be used, to operate in conjunction with this circuit, is shown in the Patent No- 1,294,498, to A. E. Lundell, issued Feb. 18, 19 19. V

Switch mechanism, keyboard and trunk indicator switch 4'01 are" each equipped with six brushes and corresponding terminal banks, while the allotter switch 121 is provided with two brushes and corresponding terminal banks. These switches have no normal position but stop in whatever position they are placed by their respective operating magnets.

The switch 510 operates the indicator, in a manner to display the designation of the selected outgoing trunk. This switch is provided with a series of stationary brushes or'wipers cooperating with a constantly rotating commutator drum having commutator segments arranged to produce the necessary combinations of impulses in the proper sequence. The commutator segments may be connected to ground or through a resistance to ground.

The keyboard consists of a single row of non-locking keys of the push-button type, and represent the digits 0 to 9. This single row of keys is used for designating the thousands, hundreds, tens and units digits of the wanted number. A separate exchange key and a wipe-out key are also of the non-locking push-button type.

The trunk indicator consists of three series of ordinary switchboard lamps ar-' ranged to indicate the hundreds, tens and units digits.

Gcneml outline of operation Referring now to Figure 1 a brief description of the organization of the system will be given.

Each manual operators position 100 to 103, is provided with the usual multiple jacks 104 in which manual subsoribers lines terminate. Besides these jacks, there ar a number of multiple-jacks 105 in which terminate trunks arranged in groups 106, 107, etc., leading to mechanical ofiices, such as 110, 111, etc. Cord circuits such as 112 are provided for connecting a jack 10 1 with a jack 105. A keyboard is indicated at 113, and a trunk indicating device is indicated at 116.

A group of connecting units 117, 118, 119, etc. is provided for the group of trunks 106, leading to the mechanical exchange 110, and-an allotter equipment 121 arranged to select an idle unit of this group may be connected to any keyboard 113 and operates under the control-of the corresponding exchange key. One allotter 121 is provided for each group of exchange connecting units having access to the various mechanical ofiices, and a common group of senders 122 is provided for the use of all operators. The switches 123 and 1241 at the mechanical exchange 110 and the circle at 125 are symbolic of the incoming and final switches and a called substation at the mechanical exchange.

The operator at position 100 receives the wanted number from the subscriber at 200 in the usual manner by connecting her telephone set with the subscribers line through the agency of the cord 112 and jack 104:. After having restored her listening key, the operator depresses the key 114; designating the wanted exchange. In response to the actuation of this key,-the allotter 121 operates to seize the preallotted idle connecting circuit 117 and starts the operators finder switch 300 to hunt for the operators key-set 113 and trunk indicator 116. The operation of the allotter results also in the starting of the trunk selector switch 400 in which the connecting circuit 117 terminates, to hunt for an idle trunk leading to the wanted mechanical exchange. The sender selector switch 401 is operated to associate an idle sender 122 with the selected connecting unit comprising 117 and 400. As soon as the connecting unit is associated with the calling operators position and the idle sender, a dialing tone is given to the operator who then begins to set up the number wanted on the key board 113. The registering device forming a part of the sender 122 is adjusted in accordance with the actuation of the keyboard, and as soon as an idle trunk has been found, the selection of the wanted line at the mechanical exchange is performed under the control of the registering device. At the same time, the number of the selected outgoing trunk is indicated on the trunk indicator 116.

lVhile the selection of the called line is proceedin the operator inserts the calling plug of tne cord circuit 112 into the jack 267 of the outgoing trunk 106, and when the selection is completed the wanted subscribers bell is rung in the usual manner. The operators finder switch and associated circuits and the trunk indicator lamps are restored to normal as soon as the operator connects her cord circuit to the outgoing trunk. The operator is thus enabled to set up a new outgoing connection regardless of whether the automatic selecting operations have been completed or not. The trunk selector and associated circuits of the connecting unit are restored to normal as soon as the mechanical selection is completed and revert to common use. The calling line is connected to the called line through cord 112 as soon as the automatic switches have completed their operation. When the subscribers have finished their conversation, the operator severe the connection in the usual manner by removing both plugs from the1r respective acks.

Detailed description of operation The detailed operation of the system, will now be described by tracing all the operations performed during the establishment of a connection. 1

When the subscriber at station 200 removes his receiver from the switchhook the line relay 202 energizes and lights the lamp 203 by means of a circuit through lts armature and front contact. On receiving this signal, the operator inserts plug 295 1nto jack 296 closing a circuit for cut-off relay 297 to extinguish the lamp 203. The operator then manipulates listening key 209 to connect her telephone set 211 to the subscribers line in the usual manner.

The operator, after receiving the wanted number from the subscriber at 200, depresses the ofiice key 114 bearing the name of the ofiice 110. The key 114 completes a circuit from grounded battery, through winding of relay 207, left-hand armature and back contact of relay 210, winding of relay 205., key 114 to ground. Relays 205 and 207 become energized and lock up through the left-hand inner front contact and armature of relay 205, resistance 230, and the left-hand armature and back con tact of relay 206. The relay 207 prepares a circuit for the trunk indicating lamps 116, the purpose of which will be hereinafter described. The relay 205 closes a circuit at its outer right-hand front contact and armature for the oflice lamps 208 that indicate to the operator the oflice for which the call is intended.

A further circuit established by the operation of relay 205 unbalances the Wheatstone bridge of allotter 121 to operate the sensitive bridge relay 301. This circuit may be traced from grounded battery, through resistance 330 and relay 301 in multiple with resistance 398, thence through resistance 331, conductor 238, armature and contact of relay 205, to ground.

The operation of relay 301 establishes a circuit for operating relays 305 and 405. This may be traced from grounded battery, through the left hand winding of relay 305, conductor 374, left hand winding of relay 405, allotter switch arm 396 and its associated contact, armature and contact of relay 301, to ground. A locking circuit is provided for relay 305 which may be traced from grounded battery through the looking winding and right hand armature and contacts of relay 305, conductor 357, right hand normal armature and contactof relay 406, to ground. Relay 305 establishes a circuit for relay 306 which may be traced from grounded battery, through the wind ing of relay 306, inner left hand armature and contact of relay 316, right hand armature and contact of relay 305, conductor 357, right hand armature and contact of relay 406, to ground. The operation of relay 306 establishes a circuit for balancing the Wheatstone bridge circuit of allotter 121 which may be traced from grounded battery, through resistance coils 330 and 332, inner right hand armature and contact of relay 306, to ground. The current flow through the Wheatstone bridge resistances 398, 331, 330 and 332 is now equalized and thus the potential in the winding of relay 301 is neutralized to cause its deenergization.

Relay 4-05 in energizing, establishes a looking circuit for itself and an operating circuit for relay 415. The locking circuit for relay 405 may be traced from grounded battery, through the right hand winding of relay 405, right hand inner armature and contact of relay 405, left hand armature and contact of relay 406, to ground. The operat ing path for relay 415 may be traced from grounded battery, through its winding to the same ground.

Relay 415, in attracting its left hand armature, establishes an obvious circuit for operating allotter switch magnet 337. This switch is controlled through its self-interrupting contacts to rotate switch arms 39.6

and 39 units.

It should be noted that the ground connected to the allotter switch terminal by relay 415 characterizes this connecting unit as busy to prevent the allotter from again selecting this connecting unit until its apparatus has been restored to normal.

The progression of switch arms 396 and 397 may bring them into contact with other busy connecting units and thus the switch magnet is repeatedly energized to rotate arms 396 and 397 until an idle connecting unit is encountered. The allotter switch will remain connected to the idle connecting unit but will not actuate the apparatus of said connecting unit until the bridge circuit is again unbalanced by the actuation of another oflice key similar to 114. The preselection of an idle connecting unit by the allotter saves the time for hunting when an office key is actuated. The .allotter 121:is now prepared to be again unbalanced by an operator desiring the use of a connecting unit in this same oflice group.

Conductors 366 and 367 extend to relays similar to relay 205 located in different operators positions. With grounds connected to the terminals of other connecting to conductors 399 and 2318, another ground may be connected to conductor 366 to again unbalance the bridge circuit and'operate relay 301. This operates the relays in a second connecting unit in the manner of this disclosure and thus a ground is connected toconductor 365 which will again balance the bridge to neutralize the potential through the winding of relay 301. When the relay in the second connecting unit, similar to relay 415, has been operated, switch magnet 337 is energized to rotate the switch arms to select another idle connecting unit. The same process of unbalancing and balancing the YVheatstone bridge takes .place as other operators require the services of these circuits.

Operators may connect ground simultaneously to conductors 238 and 366 causing the bridge circuit to be unbalanced and relay 301 to operate. A connecting unit is thus associated with an operators position and the allotter switch is propelled by switch magnet 337 in the manner previously described to select another connecting unit. However, in this instance, the ground connected to conductor 399 by the first connecting unit does not balance the bridge and relay 301 remains operated. Upon the selection of a second connecting unit apparatus in that unit is operated to connect a ground to conductor 365, thus balancing the bridge to release relay 301. It will be seen that when the two connecting units have been assigned to the two operators, a ground is connected to conductors 238 and 366 on one side of the bridge and conductors 391 and 365 on the other side of the bridge. In this manner the bridge is balanced to prepare for a third, fourth, etc. connection from operators positions to associated connecting units.

Proceeding with the description of the connecting unit, relay 306 establishes a circuit for the operating magnet 308 of the operators finder switch 300 as follows: gounded battery, winding, armature and back contact of magnet 308, outer left hand armature and front contact of relay 306, back contact and armature of relay 310, brush 325, of switch 300, inner lefthand armature and back contact to ground at the relays 205 provided at other operators position. The magnet 308 is thereby through its self-interrupting armature and back contact, caused to step the operators finder switch 300 forward until it finds the desired operators position at which the relay 205 is energized.

During the operation of the operators finder switch, a circuit is completed for relay 310 in a branch of the driving circuit of magnet 308, this circuit extending through the winding of relay 310 and the inner left-hand armature and front contact of relay 306, to ground. This relay is, however, shunted by direct ground at the back contacts of relays 205 associated with nondepressed office keys. When the test brush 325 engages a terminal at which the office key has been depressed, ground through resistance 230 will be found on this contact. Fhe presence of resistance 230 prevents fur ther operation of magnet 308 and is so designed as to allow relay 310 to operate. The resistance of relay 310 is also great enough to prevent further operation of magnet 308.

Relay 310 closes a circuit from grounded battery, through the winding of relay 207, left-hand armature and back contact of relay 210, the winding, inner left-hand front contact and armature of relay 205, brush 325, armature and front contact of relay 310, and the winding of relay 313 to ground. Relay 313 locks up through a branch circuit from brush 325, left-hand front contact and armature of relay 305, left-hand armature and front contact and winding of relay 313 to ground.

The operators keys and trunk indicator equipment are now connected to the connecting unit 117, relays 305 and 405 being operated.

Upon its energization, the relay 405 establishes a circuit for operating magnet 408 of the sender selector 401 as follows: grounded battery, winding, armature and back contact of magnet 408, left-hand contact and armature of relay 405, left-hand back contact and armature of relay 410, brush 425, and terminals and leads of busy senders left-hand front contact and armature of relay 701 to ground at the right hand intermediate normal contact and armature of relay 922, or a ground through winding of relay 413. This causes the sender selector magnet 408 to step the switch 401 forward until an idle sender is found, at which time the sender selector magnet 408 is prevented from continuing its operation by the presence of grounded battery at the outer righthand armature and back contact of relay 701 through the high resistance winding of relay 702, lead 625 and brush 425. Relay 410 is now energized over a circuit as follows: grounded battery, through winding and contacts of magnet 408, left-hand con tact and armature of relay 405, winding of relay 410, outer right-hand armature and front contact of relay 405 to ground. The resistance of the winding of relay 410 is such as to prevent the further operation of the sender selector magnet 408. The brushes of the sender selector switch 401 will therefore come to rest on the terminals representing the first idle sender. The relay 410 causes the operation of relay 413 over a circuit as follows: grounded battery, righth-and armature and back contact of relay 701, high resistance winding of relay 702, lead 625, brush 425, left-hand armature and front contact of relay 410, winding of relay 413 to ground. This ground at relay 413 makes the sender busy until relay 701 operates when the busy ground is received through the left-hand front contact and armature of relay 701 from the normal contact and armature of relay 922.

Relays 313 and 413 being energized, the following circuit is established for relay 315: grounded battery, relay 315, lead 356, right-hand armature and front contact of relay 410, lead 351, inner right-hand front contact and armature of relay 313 to ground. he relay 315 closes a circuit from grounded battery, through the winding of relay 316, left-hand armature and front contact of relay 315 to ground. Relay 316 becomes energized and closes a locking circuit for itself through its right-hand front contact and armature, lead 358, to ground at the left-hand back contact and armature of relay 406. The relay 316 opens the operating circuit for the relay 306 but, inasmuch as this relay 306 is slow to deenergize and relay 316 is quick in action, a circuit will be established for a short interval from dialing tone source 328, through the outer right-hand front contact and armature of relay 306, the outer left-hand front contact and armature of relay 316, conductor 452, brush 329, lead 334, armature and back contact of relay 221, primary winding of induction coil. 223 to grounded. battery and ground. This dialing tone is transmitted inductively to the operators telephone so over a circuit as follows: ground, the induction coil of the operators telephone set 211, outer left-hand armature and front contact of exchange relay 205, secondary winding of induction coil 223 to grounded battery. This dialing tone indicates to the operatorthat an idle sender has been connectee to the keys 113 and that registration of the wanted line number may begin regardless of whether or not the trunk selector has found an idle trunk.

The operation of the trunk selector is accomplished under the control of a relay 415 which operates as soon as relay 405 is operated over a circuit as follows: grounded battery, relay 415, inner right-hand front contact and armature of relay 405, back contact and left-hand armature of relay 406 to ground. The relay 415 closes a circuit for the trunk selector operating magnet 416 from grounded batter through the wind ing, armature and back contact of magnet 416, right-hand front contact and armature of relay 415, left-hand back contact and armature of relay 417, brush 423, lead 454 to ground at the relay 502 of busy outgoing trunks or to ground at the left-hand front contact and armature of relay 417 of busy trunk selector. This circuit causes the operation. of the operating magnet 416 which thereupon causes the stepping of the brushes of the trunk selector 400 until an idle trunk is found, at which time the operation of magnet 416 is discontinued. The relay 417 is now operated through a circuit as follows grounded battery, inding, armature and back contact of magnet 416, inner righthand armature and front contact of relay 415, relay 417, outer right-hand front con tact and armature of relay 415, to ground. During the operation of the magnet 416, relay 417 was shortcircuitcd by the ground at relays like 502. The resistance of relay 417 is such as to prevent suthcient current from flowing through the magnet 416 to operate the magnet and thus the switch is stopped with its brushes resting on the terminals of the first idle trunk encountered and relay 41.7 connects a ground to brush 428 through its left-hand front contact and armature to establish a busy condition for this trunk.

The relay 417 also establishes an energizing circuit for relays 320 and 422. The circuit for relay 320 is as follows: grounded battery, winding of relay 320, middle right hand armature and front contact of relay 313, lead 355, inner right-hand front contact and armature of relay 417 to ground. The circuit for relay 422 is from grounded battery, through winding of relay 422, inner left-hand armature and front contact of relay 413, leads 359 and 355, to ground at relay 417. The relay 422 connects the leads 447 and 448 of the chosen outgoing trunk through brushes 430 and 431 of the trunk selector 400, armatures and front contacts of relay 422, brushes 432 and 433 of the sender selector 401 to the fundamental circuit leads 620 and 621 of the sender 122. The relay 320 connects the operating leads 342 and 345 for the trunk indicator through brushes 341 and 344, leads 340 and 343 leading to the indicator 116. The leads 342 and 345 are connected through leads 441 and 445 to the trunk indicator operating mechanism at 510. The relay 320 closes a circuit for relay 420 from battery through the winding of relay 420, lead 352, right-hand armature and front contact of relay 320 to ground. Relay 420 establishes a locking circuit for itself through its left-hand front contact and armature, the left-hand back contact and armature of relay 406 to ground. The r lay 420 also establishes a circuit for relay 505 from grounded battery, through relay 406, right-hand armature and front contact of relay 420, brush 447, lead 453, the low and high resistance windings of relay 505 to ground. Due to the high resistance of relay 505, relay 406 is not operated at this time but relay 505 is operated. The relay 505 extends through its left hand armatures and front contacts, the fundamental circuit leads 447 and 448 to the outgoing trunk leads 507 and 508. The actuation of the indicator 116 in accordance with the number of the chosen trunk, which it is assumed is 767, will now be described.

It will be remembered that the'connection through to the trunk indicator iscompleted as soon as the trunk selector 400 finds an idle trunk, and before the relay 420 is operated. Since the idle trunk selected is 767, the lead 521 is connected directly to ground, and lead 522 is connected to ground through a resistance. If the hundreds digit of the trunk number had been some other number,

a different combination of electricalpotentials would have been connected to the leads 521 and 522. Due to the ground on lead 521 a circuit is closed from grounded battery, through the winding of relay 601,. winding of relay 602, lead 252, outer left-hand back.

contact and armature of relay 226, lead 340, brush341, inner left-hand front contact and armature of relay 320, lead 342, brush 440. lead 441, lead 521 to ground. Relays 601 and 602 are both energized in this circuit. Relay 601 is marginal and would not have been pulled up if the ground applied at the contacts of relay 509 had included a resistance. Relay 602 is sensitive however and will respond whenever a circuit is closed through it regardless of whether a resistance is included at contacts of relay 509 or not. At the same time a circuit is established from grounded battery through the winding of relay 603, winding of relay 604, lead 251, inner left-hand back contact and armature of relay 226, lead 343, brush 344, outer lefthand front contact and armature of relay 320, lead 345, brush 443, lead 445, the inner upper armature and back contact of relay 509 and lead 522 to ground through the resistance included in lead 522. Relay 604 is a sensitive relay and is energized in this circuit, but since relay 603 is marginal it does not energize. The relays 601, 602 and 604 prepare a circuit for the hundreds digit lamp, but this lamp will not be lighted at this time but awaits the operation of certain relays to take place after the tens and units lamps have been selected, as will be hereinafter described. These hundreds digit relays establish locking circuits for themselves from grounded battery, through their respective locking windings to the ground at the relay 207.

As soon as the hundreds digit relays are locked up a'circuit is established for the relays 227 and 226 as follows: grounded battery, windings of relays 227 and 226 in parallel, lead 260, inner left-hand armature and front contact of relay 602 or outer right-hand armature and front contact of relay 604, lead 259, right-hand make beforebreak contacts of relay 226, to brush 511 and ground at commutator segment 512. Brush 511 and segment 512 are the first active elements in the rotary impulser switch 510 in regards to establishing an indication for the tens and units digits. The relay 226 causes the leads 340 and 343 to be switched over to leads'254 and 253, respectively. By this time relay 505 has operated and a circuit is established through the same brush 511 and commutator contact 512 that caused the operation of relays 227 and 226 for the operation of relay 509 as follows: fromv grounded battery, through winding of re-.

lay 509, outer right-hand armature and front contact of relay 505, continuity contact of relay 509, through the brush 511 and commutator segment 512 to ground. This circuit energized relay 509 and a locking.

circuit is established for relay 509 from grounded battery, through winding of relay 509, outer armature and front contact of relay 505, lower front contact and armature of relay 509, to ground. The relay 509 extends the leads 441 and 445 through to brushes 513 and 514, respectively, of the rotary impulser switch 510. A connection is now completed from the rotary impulser switch 510 to the trunk indicator so that the indication of the tens and units digits of the chosen trunk may be effected at the trunk indicator by the continuous rotation of the rotary switch 510, a certain sequence of impulses being sent from the commutator segments of the drum of the rotary switch 510 through these leads to the relays 231 and 229, respectively. I

The rotary impulser switch 510 is preferably of cylindrical form, but to make the disclosure more readily understood, the cylinder has been developed into a plane rectangular surface. The rotary switch may be constantly driven from any suitable source.

It should be not-ed that regardless of the position of the rotary impulser switch 510 at the time relay 505 is energized no pulses will be sent to the indicator relays until segment 512 is engaged by brush 511. A circuit is thus established to energize relay 509 and the contacts of relay 509 establish energizing paths for the indicator relays as the impulser brushes engage the segments.

One of the first segments of the rotary switch 510 that will be associated with the brush 513 is connected to ground. This will complete a circuit for relay 231 from grounded battery through the winding of relay 231, lead 254, and outer left-hand armature and front contact of relay 226 through the switches 300 and 400 to brush 513 and segment 531 to ground. Relay 231 is energized in this circuit. At the same time that brush 513 engages segment 531, brush 514 is brought into engagement with segment 535. A circuit is then completed for relay 229, extending from grounded battery, winding of relay 229, inner left-hand armature and front contact of relay 226, conductor 343, brush 344, outer left-hand armature and front contact of relay 320, brush 443, inner upper armature and front contact of relay 509, conductor 524, brush 514, segment 535 to ground. Relay 229 is energized in this circuit and switches through the impulse leads to the units lamp controlling relays. At the same time that relays 229 and 231 are energized, brush 526 engages segment 537 to energize relay 607 of the tens group andrelay 611 of the units group. The circuit of relay 607 extends.

from grounded battery, left-hand winding of relay 607, conductor 245, outer left-hand armature and front contact of relay 231, conductor 232, brush 526, segment 537 to ground. The circuit of relay 611 extends.

from grounded battery, left-hand Winding of relay 611, conductor 250, outer left-hand armature and front contact of relay 229, conductor 232 to ground, as described. Relays 607 and 611, upon energization, lock up to conductor 286 which is grounded at the left-hand armature and front contact of relay 207.

The impulse switch 510 continues to rotate and when the next row of contacts is brought into engagement with the brush set, brushes 513 and 514 engage contacts 532 and 536. Relays 229 and 231 are again energized. At the same time brush 527 engages segment 538 to energize relay 609 in the tens group and relay 613 in the units group. The circuit of relay 609 extends through the inner left-hand armature and front contact of relay 231 to ground through brush 527 over conductor 288. The circuit of relay 613 extends over conductor 2&7 and the inner left-hand armature and front contact of relay 229 to ground over the same path. Relays 609 and 613, upon energization, lock up to grounded conductor 236. The next horizontal row of contacts is brought into operative relation with the brush set. Brushes 513 and 51% do not engage contacts. Therefore relays 229 and 231 are deenergized at the time that brush 528 engages segment 589 and no impulses are sent to the controlling relays of either the tens group or the units group.

Then the next row of contacts is brought l'HbO engagement with the brush set, brush 513 engages segment 533 to energize relay 231, as previously described. Since brush 514 does not engage a segment, relay 229 is not energized at this time. Therefore, when brush 529 engages segment 540, an impulse will be sent to the tens controlling relays only. This impuse pulls up relay 608 over a circuit extending from grounded battery, left-hand winding of relay 608, conductor 242, outer right-hand armature and front contact of relay 231, conductor 285, brush 529 and segment 540 to ground. Relay 608 is energized and locked up to grounded conductor 286.

The impulser 510 continues its rotation and when brush 530 engages segment 541, a circuit is completed from grounded battery, left-hand winding of relay 206, armature and front contact of relay 227, brush 530, segment 541 to ground. Relay 206 is energized, and locks up through its right- "hand winding and inner right-hand :armature and front contact to grounded conductor 236. 7 At the same time, a-circui t is completed from grounded battery, winding of relay 228,. inner right hand armature and front contact of relay 206 to ground to energize relay 228. Relays 206 and 228, at

their various :armatures, controlthe ap'lication of ground and battery to. the leads -7Conneet conductor 521 to 441, connectconductor 522 which control the lighting of the number indicating lamps.

The circuit for the N o. 7 lamp in the hundreds group extends from grounded battery through lamp 7, outer left-hand armature and back contact of relay 603, outer right hand armature and front contact of relay 601, outer left-hand armature and front contact of relay 604, outer left-hand armature and front contact of relay 602, conductor 258, to ground at the right-hand armature and front contact :of relay 228. The circuit for the N o. 6 lamp in the tens group extends from grounded :battery, outer right-hand armature and front contact of relay 206, conductor 2 10, outer left-hand armature and front contact of relay 608, lamp 6, inner left-hand armature and front contact of relay 607, lett-hand armature and front contact of relay 609,'inner right-hand armature and front contact of relay 608 to grounded conductor 236. The circuit for the No. '7 lamp in the units group extends from grounded battery, middle left-hand armature of relay 228, conductor 256, outer left-hand armature and back contact of relay 612, left hand armature and front contact of relay 613, left-hand armature and front contact of relay 611, lamp 7, inner right-hand armature and back contact :of 1 relay 612 to grounded conductor 236, As .a result of these circuits, the lamps are lighted to indicate that the number of the idle outgoing trunk selected is 767.

V The following tabulations give in graphic form the Various relay combinations obtainable with the indicating device shown in Fig. 7 for indicating the various digits of a trunk designation.

Hand-reds 1-Conneet conductor 521 to 445-conductor 522 open.

Relays 603, 604 and 605 operated.

Q- COnneet eonductor521 to 441and 4A5.

Relays 601, 602, 603, 604 and 605 operated.

3-Connect conductor 522 to 441eonductor 521 open.

Re1ay1602 operated 4-Connect conductor522 to 445-conduetor 52l-open. .Re1ay604'operated. V

5Connect conductor 522 to 441 and-44=5.

Relays 602 and 604 operated.

6ConnZct conductor 522 to .441, connect conductor 521 to A Re1ays.(302,*603,-604 and 605 operated.

Relays n, 602rand e04 operated.

8Not used. 7

9-Not used.

.iTcns 0-Connect conductor 523 to brush0.

Relay 608 operated.

:1Conductor.523 open (not connected).

A11v relays normal.

2Conneet.conductor523 to brush 2. I

Relays-607 and 608 operated. V

3Connect conductor 523 to brush 3.

Relay 607 operated.

4Connect conductor 523 to brush 4.

Relays 608 and 609 operated.

5Connected conductor 523 to brush 5.

Relay 609 operated.

6-Conneet conductor 523 to brush 6.

Relays 607, 608 and 609 operated.

7Connect conductor 523 to brush 7.

Relays 607 and 609 operated.

8Conneet conductor 523 to brush 8.

Relays 608 and 610 operated.

9Connect conductor 523 to brush 9.

Relay 610 operated.

Units 0Connect conductor 524 to brush 0.

Relay 612 operated.

J.Conduetor 524 open (not connected).

All relays normal.

2-Connect conductor 524 to brush 2.

Relays 611 and 612 operated.

3Connect conductor to brush 3.

Relay 611 operated.

4Co-nnect conductor 523 to brush 4.

Relays 612 and 613 operated.

5-Conncct conductor 524 to brush 5.

Relay ($13 operated.

6(.onneet conductor 524 to brush 6.

Relays 611, 612 and 613 operated.

7Counect conductor 524 to brush 7.

Relays 611 and 613 operated.

8-Conneet conductor 524 to brush 8.

Relays 612 and 614 operated.

9-enncct conductor 524 to brush 9.

Relay 61.4 operated.

To vary the hundreds number, a cross connection must be assumed between conductor 521 and either of the upper normal contacts of relay 509, also between conductor 522 and either of the same upper normal contacts. The interchanging of conductors 521 and 522 coupled with the omitting of one or both of these conductors makes possible the combinations given in the tabulation. v

To vary the trunk number indications for tens and units, a cross connection must be assumed. between conductors 523 and 524 to any one of brushes 0, 2, 3, 4, 5, 6, 7, 8 and 9 as shown in the tabulations. As outlined in the descriptive matter of this specification,

relays 509, 226 and 227 are operated when the relays for the hundreds digit have been operated and locked. These relays function as a transfer of control so that a minimum number of conductors can be used extending to the number indicating apparatus thus transferring conductors 441 and 445 to conductors 523 and 524 under the control of the pulsing mechanism to operate relays 231 and 229 in synchronism with the pulses impressed on conductors 526, 527, 528 and 529 by commutator segments 537, 538, 539, and 540 of the pulsing mechanism.

Since the impression of ground potential on the conductors for operating relays 229 and 231 is synchronized with the impression of ground potential on a conductor for opor 524 to a brush contacting with any segment in a horizontal plane with segment 537 will operate relays 607 or 611. Also the connection of conductors 523 or 524 to a brush contacting with any segment in a horizontal plane with 538 will operate relays 609 or 613.

It is thought that from the foregoing description, the manner in which any desired number may be set upon the indicator will be readily understood by one skilled in the art.

The operator locates the corresponding outgoing trunk jack 267 corresponding to trunk No. 767 and inserts therein the calling plug 265 of the cord circuit 112. This lights the supervisory lamp 266 over a circuit established as follows: Grounded battery, lamp 266, sleeve contacts of plug 265 and jack 267, winding of relay 520, to ground. The relay 520 establishes a circuit for relay 502 as follows: grounded battery, winding of relay 502, inner right-hand front contact and armature of relay 505, front contact and armature of relay 520 to ground. Relay 502 energizes and establishes a locking circuit for itself through its inner right-hand front contact and armature to ground at the front contact and armature of relay 520. The operation of relay 520 causes the trunk indicator to be restored to normal.

The restoration begins with the energization of relay 406 over a circuit as follows: grounded battery winding of relay 406, right-hand armature and frontcontact of relay 420, brush 447, lead 453, the low resistance winding of relay 505, front contactand armature of relay 520 to ground. The energization of relay 406 breaks the locking circuit for relay 305 and as relay 305 deenergizes, the holding circuit for relays 207, 205 and 313 is broken. These relays are all deenergized due to the fact that the relay 206 is still energized and the original looking circuit for these relays has been broken at the left-hand armature and back contact of relay 206. The deenergization of relay 205 breaks the energizing circuit for the exchange lamps 208, and the original energizing circuit for relay 301. The deenergization of relay 207 breaks the locking circuit for the various relays of the trunk indicator and all of these relays are released. The deenergization of relay 313 breaks the circuit of relay 320.

The de-energization of relays 205 and 313 opens both of the balancing circuits for the allotter 121. It should be noted that relay 313 is slow to deenergize in comparison with relay 205 so as to prevent the energization of relay 301 a second time by the ground at relay 205 and the consequent starting of a connecting unit.

The operator may now prepare a different sender and outgoing trunk provided all the digits of the wanted number have been registered but regardless ofwhether or not the registers have completed their selection at the mechanical ofiice. It should be remembered that the operator starts to set up the wanted number on the key set 113 as soon as she receives the dialing tone, which takes place before or simultaneously with the operation of the trunk selector 400 and the displaying of the selected trunk on the indicator 116,

Operation of the keys Before describing the registering of the number and the subsequent selection of the wanted number at the mechanical office, it should be understood that the various series of impulses that are to be sent from this exchange for the selection of the proper number at the automaticexchange are not in ac cordance with the decimal system but that a certain translation scheme is employed which is similar to that shown in the mentioned application by A. E. Lundell, Serial No. 139,511, filed December 29, 1916, and a patent to A. E. Lundell and F. A. Stearn, No. 1,345,016, issued June 29, 1920. In the system described in these applications m-e chanical exchange has a capacity of ten thousand subscribers lines. The subscribers lines are divided into five groups of two thousand each and each group of two thousand is divided into four groups of five hundred each; each five hundred group is di- Vided into five groups of one hundred each. The impulses representing the thousands and hundreds digits bring about various selections which will extend the incoming trunk leads to a group of one hundred lines in which the tens and units selections will be made in accordance with the decimal system.

The series of impulses controlled by the thousands and hundreds keys in the wanted number 4789 used in this description, are as follows: For the thousands digit No. 4, three impulses are sent which determine in which group of two thousand a selection shall be made. The thousands and hundreds digits jointly control the sending of two impulses to control the selection of the proper group of 500 lines. The hundreds digit N o. 7 will then control the sending of three impulses to determine in which of five groups of one hundred each selection is to be made. In a ten thousand line exchange, the thousands impulses are from 1 to 5 to select a group of two thousand out of a total of five groups, the hundreds impulses are from 1 to 4 to select a group of five hundred out of a total of four groups in a two thousand group, followed by from 1 to 5 impulses to select a group of one hundred out of a total of five groups in a five hundred group.

The setting up of the digits of the wanted number on the operators key set 113 will now be described. It will be remembered that at the time the connecting unit 117 has found an idle sender, a dialing tone was transmitted to the operator indicating that the setting up of the number of the wanted subscriber may take place. It should also be noted that this setting up of the number may begin before the connecting unit 117 has found an idle outgoing trunk, that is, the setting up of the number may take place simultaneously with the operations necessary to find an outgoing trunk.-

It has been assumed that the subscribers line having the number 4789 was to be selected. As soon as an idle sender was associated with the connecting unit a control circuit was completed from the operators keyboard 113 to the register and control equipment. This controlling circuit comprises Jhree leads that are connected to the thousands register relays, 802, 803, 804 and 805. A path extends from grounded battery, through a winding of relay 802, lead 720, outer right-hand back contact and armature of relay 712, winding of relay 715, lead 622, brush 490, lead 450, inner righthand armature and contact of relay 315, conductor 450, brush 353, lead 346, to keys 113. A second path may be traced from grounded battery, windings of relays 804 and 803 in series, lead 721, middle righthand back contact and armature of relay 712, lead 623, brush 455, lead 451-, middle right-hand armature and contact of relay 315, lead 451, brush 354, lead 347 to keys 113. A third path leads from grounded battery, through a winding of relay 805, lead 722, inner back contact and armature of re lay 712, inner right-hand back contact and armature of relay 701, lead 624, brush 456, lead 452, outer right-hand armature and contact of relay 315, lead 452, brush 329, lead 334, right-hand armature and back contact of relay 221, induction coil 223, to grounded battery.

Upon the depression of key No. 4 for the thousands digit, a circuit is established from grounded battery, through the left hand winding of relay 802, the left-hand front contact of key No. 4 and resistance 260, to ground. Another circuit is established for relays 804 and 803 from grounded battery, through the left hand windings of relays 804 and 803, and the right-hand contact of key No. 4, to ground. 3110 to the fact that the resistance 260 is in the circuit for the marginal relay 802, it does not operate but there is sur'licient current passing through this circuit to operate relay 715. The relay 715 establishes a circuit for counting relay 705 as follows: grounded battery Winding of relay 705, inner left-hand back contact and armature of relay 704, front contact and armature of relay 715, to ground. The relays 804 and 803 become energized and es tablish locking circuits for themselves from grounded battery through their right-hand front contacts and armatures, normal contact and armature of relay 7 01, to ground, at relay 922. As soon as the thousands key is released, the relay 715 becomes deenergized and removes the shunt path from the winding of relay 704, whereupon relay 704 becomes energized and relay 705 locked up by current flowing from grounded battery, through windings of relays 705 and 704, right-hand front contact and armature of relay 705, left hand normal contact and armature of relay 7 01, to ground, at the righthand intermediate normal contact and armature of relay 922. The relay 704 establishes through its right-hand inner armature and front contact an energizing circuit for relay 712. The relay 712 causes the extension of the three controlling leads 622, 623 and 624 from leads 720, 721 and 722 to leads 723, 724 and 725, respectively.

The depression of the hundreds digit key No. 7 causes a circuit to be established from grounded battery, through the left hand winding of relay 806, the left-hand contact of key No. 7, and the low resistance winding of relay 221, to ground. This energizes relays 806 and 221, and due to the energization of relay 221 a circuit is established from grounded battery, through the winding of relay 809, the armature and front contact of relay 221 to ground. This circuit energizes relay 809, and relays 806 and 809 are locked up over a circuit from grounded battery, through their respective locking windings, left hand normal contact and armature of relay 701, to ground at relay 922. The

relay 715 is again energized but is now in series with relay 806. The relay 715 completes a circuit for relay 707 as follows: grounded battery, winding of relay 707, lefthand back contact and armature of relay 706, inner left-hand front contact and armature of relay 704, front contact and ar1nature of relay 715, to ground, to energize relay 707.

As soon as the hundreds digit key is released, the relay 715 becomes deenergized and permits the energization'of relay 706, the circuit being closed from grounded battery, through the windings of relays 707 and 706 in series, front contact and armature of relay 707, left-hand normal contact and armature of relay 701, to ground, at relay 922. The relay 706 establishes a circuit for relay 713 from grounded battery, through relay 713, right-hand front contact and armature of relay 7 06 to ground. The relay 713 causes the extension of the three controlling leads 622,623 and 624 from leads 723, 724 and 725 to 727, 728 and 729, respectively.

Upon the depression of the tens digit key No. 8, a circuit is established for relay 810 from grounded battery, through the winding of relay 810, the left-hand contact of key No. 8, low resistance winding of relay 221, to ground. Another circuit is extended from grounded battery through the left hand windings of relays 812 and 811 in series, the right-hand contact of key No. 8 and low resistance winding of relay 221, to ground. Relay 221 is operated and a circuit is established for relay 813 from grounded battery through the left hand winding of relay 813,.

right-hand armature and front contact of relay 221, to ground. The relays 810, 811, 812 and 813 are operated and establish looking circuits for themselves from grounded battery, through their locking windings, right-hand front contacts and armatures, left-hand normal contact and armature of relay 701, to ground at relay 922. Relay 715 is now energized in series with relay 810 and closes a circuit from grounded battery, through the winding of relay 709, left-hand back contact and armature of relay 708, lefthand front contacts and armatures of relays 706 and 704 in series, through front contact and armature of relay 715, to ground. When the tens digit key is released, relay 715 deenergizes and relay 708 is energized and locked up in series with relay 709 from grounded battery, through the windings of relays 709 and 708, front contact and armature of relay 709, left-hand normal contact and armature of relay 701, to ground at rela 922.

T e relay 708 establishes a circuit for re lay 714 as follows: grounded battery, winding of relay 714, right-hand front contact and armature of relay 7 08, to ground. This energizes relay 714 whose armatures switch the controlling leads from leads 7 27 728 and 729 to leads 731, 732 and 733 and the circuits are now ready to receive the units impulses.

In response to the depression of the units digit key No. 9, the following circuits are established: grounded battery, left hand winding of relay 814, relay 715, through to lefthancl contact of key No. 9, high resistance winding of relay 221, to ground. Due to the high resistance in this circuit, the relay 814, which is marginal, does not energize but relay 221 does energize. A second circuit is established from grounded battery, through the left hand windings of relays 816 and 815 in series, through to the righthand contact of key No. 9, the low resistance winding of relay 221, to ground. The relay 221 establishes a circuit for relay 818 as follows: grounded battery, left-hand winding of relay 818 through to right-hand armature and front contact of relay 221, to ground. Relays 815, 816 and 818 are energized and 

